Overview of Bladder Outlet Obstruction

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Bladder outlet obstruction (BOO) is a problem in which the flow of urine is partially or completely blocked. This produces a number of symptoms, including diminished urine flow, pelvic pain, and bladder discomfort. Chronic BOO can result in complications such as infections, bladder stones, loss of bladder function, and kidney failure. Though the condition can affect males and females, bladder outlet obstruction occurs most often in older men.

The most common issues in men that can cause BOO include prostate problemstumors of the bladder, and urethral narrowing from scarring or strictures. Often, diagnostic testing is necessary to identify the cause of BOO, and medical or surgical treatments can be used to relieve the obstruction.

Older male patient talking with doctor over tablet
John Fedele / Getty Images


Typically, bladder outlet obstruction begins with mild, bothersome symptoms that gradually worsen over time. Depending on the severity, the symptoms may be intermittent; you might only experience them once in a while, rather than every time you urinate.

The symptoms may occur more abruptly if there is an infection within the prostate, large tumor within the bladder, or nerve damage from recent stroke or back procedures.

Signs of a bladder outlet obstruction include:

  • Difficulty maintaining a forceful urinary flow
  • Stop-and-go flow
  • Reluctance to urinate, also known as hesitancy
  • Terminal dribbling, characterized by slow dribbling of your urine near the end of the stream
  • A strong urge to urinate
  • Pelvic pain
  • Frequently urinating tiny amounts of fluid
  • A feeling of fullness and a sensation of urine remaining in your bladder after you've peed

As the obstruction becomes more severe, you may have to strain your muscles with increasing effort to push urine past the blockage.


Over time, you can develop serious health problems due to bladder outlet obstruction. In fact, neglecting early symptoms may lead to irreversible complications.

Issues that can develop as a consequence of BOO include:

  • Bladder stones
  • Urinary infections (can be recurrent)
  • Urinary incontinence
  • Kidney failure
  • Bladder dysfunction

Prolonged BOO may cause irreversible kidney failure if it is not treated, as the fluid backflows into the ureter and the kidneys.


The bladder is a muscular cavity that holds urine. The bladder expands as it fills with urine and contracts when it's time to empty. It is located in the lower abdomen behind the pelvic bone. The urethra is a thin muscular tube through which urine travels from the bladder to the outside of the body. (In men, the urethra is inside the penis. In women, the urethra is shorter and the opening is near the vagina.)

Bladder outlet obstruction is usually caused by physical pressure at the bladder outlet (lower base of the bladder leading to the urethra) or along the urethra. BOO can also be caused by physiologic side effects from conditions like Parkinson's, multiple sclerosis, strokes, and back injuries.

With BOO, the bladder contracts as usual to initiate the stream of urine, but the outlet is partially blocked.

A number of conditions can lead to bladder outlet obstruction. Medical problems that cause pressure, trauma, inflammation, or scarring of the bladder outlet or the urethra can be to blame.

BOO can develop as a result of:


Your healthcare provider will start by taking a medical history, asking questions about your urinary symptoms and other health issues such as weight changes, bowel fluctuations, fluid intake, symptoms of sexually transmitted diseases (e.g., itching, burning, pain or discharge in the genital area), and back or pelvic trauma.

Your healthcare provider will look at your abdomen and place light pressure on it to assess for swelling or discomfort. A physical examination can help your medical team spot any visible signs of an STD, such as redness or discharge.

A man with symptoms of BOO may also need to have a digital rectal examination where the healthcare provider can estimate the size of the prostate and look for any nodules that are concerning for cancer.

Labs and Tests

If you have symptoms such as urinary hesitancy or bladder fullness, your medical team may want you to have a number of tests to identify the problem.

Possibilites include:

  • Urine test: Glucose in the urine is a sign of diabetes. Blood could be a sign of infection, recent instrumentation, or underlying cancer. Bacteria is a sign of infection. Protein and cells may be indicative of issues with your kidneys.
  • Post Void Residual: This is where an ultrasound is done of your bladder to check for residual urine after you have urinated.
  • Abdominal Imaging: If there is an additional concern, your healthcare provider may order additional imaging like a CT scan, MRI, or renal scan.
  • Cystoscopy: This test involves the placement of a tube into the urethra and the bladder to visualize the inside of these structures with a camera.

Differential Diagnoses

Diabetes can cause urinary frequency, and it may not be obvious whether your urinary changes are caused by the disease or a bladder outlet obstruction.

Neurological bladder dysfunction can result in a decreased ability to urinate and bladder distension, which may feel similar to the symptoms of BOO.

Diagnostic tests can help distinguish between these causes.


Depending on the cause, you may need interventional treatment for your bladder outlet obstruction. Treatments are generally geared towards what your healthcare provider feels is the main cause of the BOO.

In men, the most common cause is an enlarged prostate, which could be treated with medications that relax or shrink the prostate, minimally invasive procedures like prostate lifts or steam vaporization that open up the prostate channel, or surgeries where the prostate is resected.

If the issue is a tumor in the bladder, minimally invasive surgeries are done to remove the tumor, which can then lead to a better urine stream. Additional procedures or interventions may be needed for the bladder tumors.

If the issue is scarring in the urethra from trauma or infections, your healthcare provider may recommend minimally invasive procedures to open up the scarring through the urethra with a small knife or ballon. In severe cases, your healthcare provider may recommend a full reconstruction of the urethra.

Catheter Placement

In acute or emergency cases, you'll have a catheter placed into your bladder via your urethra to help empty your bladder. A catheter could also be placed after procedures are done to open up your prostate channel or remove scarring from your urethra.

In rare cases, if the bladder fails to work, you'll need to keep a catheter in place at all times or place a catheter into the bladder to help it empty several times a day. Healthcare providers try to avoid the need for chronic catheterization by catching and treating BOO early.


There are medications that can be used to help control urine flow. For example, Flomax (tamsulosin) and others may help with symptoms of urinary retention, but they do not relieve the obstruction.

A Word From Verywell

Bladder outlet obstruction is a serious issue that should not be ignored. It can be effectively managed, however. If you have problems with urination, it is important that you discuss your concerns with your healthcare provider, as bladder problems typically worsen if not treated.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Laura Newman
Laura Newman is an award-winning journalist with expertise in clinical medicine, health policy, urology, oncology, neurology, and targeted therapies.